Magnetic resonance appearance of the kidneys in paroxysmal nocturnal hemoglobinuria.

A diagnosis of paroxysmal nocturnal hemoglobinuria may be suggested with magnetic resonance imaging, based on the massive renal cortical hemosiderosis that occurs in this disease. A diffuse bilateral depression of renal cortical signal intensity will be observed that is caused mainly by a shortening of the T2 relaxation time of renal cortical protons by the paramagnetic effect of the locally increased ferric ion concentration in the proximal convoluted tubule.